Electroluminescent display device and thermal transfer donor film for the electroluminescent display device

ABSTRACT

The invention is directed to an organic electroluminescent (EL) display device having an improved light extracting efficiency due to a photonic crystal layer formed proximate one side of a stack. Among other elements, the stack may include a first electrode formed on a substrate, an organic light emitting layer formed above the first electrode, and a second electrode formed above the organic light emitting layer. Additionally, the photonic crystal layer may be configured to correspond to a wavelength of colored light. An organic EL display device having an improved light extracting efficiency may be manufactured using a thermal transfer donor film to adhere the photonic crystal layer to the stack.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 10/992,219, filed on Nov. 19, 2004 and claims the benefit ofKorean Patent Application No. 2003-85819, filed on Nov. 28, 2003, in theKorean Intellectual Property Office, which are herein incorporated byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an organic electroluminescent (EL)display device and a thermal transfer donor film used in manufacturingan organic EL display device. More particularly, the invention relatesto an EL display device having a high efficiency of light extractionfrom an organic light-emitting portion. The higher efficiency is causedin part by a photonic crystal layer located directly on a stack formedon the substrate. Additionally, a laser induced thermal transfer donorfilm for the EL display device is used to form the photonic crystallayer on the stack.

2. Description of the Related Art

An electroluminescent (EL) display device forms viewable images byreflecting or shining light through an organic thin film material (e.g.,a light emitting portion) sandwiched between millions of anodes andcathodes that are formed on opposing surfaces of two parallel glasssubstrates. Applying a voltage difference to each anode/cathode pair(e.g., pixel) alters the physical properties of the organic lightemitting layer. When the voltage differences are applied in discreteamounts, various shades of colors are produced. Organic EL displaydevices are popular because they are driven by low voltages, are lightand thin, and offer wide viewing angles and fast response times.

As mentioned above, the light-emitting portion of the EL display deviceincludes an anode, a light-emitting layer, and a cathode sequentiallyformed on each other. The light-emitting layer may include an emittinglayer (EML) in which exitons are formed by the recombination of holesand electrons to create light. An exiton is an electrically neutralexcited state of an insulator or semiconductor, often regarded as abound state of an electron and an electron hole (“hole”). A hole is avacant position left in a crystal by the absence of an electron. The EMLmay further include: an electron transport layer (ETL) located betweenthe cathode and an emitting layer to transport holes and electrons moresmoothly to the emitting layer thereby increasing emitting efficiency; ahole transport layer (HTL) located between the anode and the emittinglayer; a hole injection layer (HIL) located between the anode and thehole transportation layer; and an electron injection layer (EIL) locatedbetween the cathode and the electron transportation layer. Exemplaryconventional light-emitting layers can be composed of copperphthalocyanine (CuPc), N,N′-Di(naphthalene-1-yl)-N,N′-diphenyl-benzidine (NPB), ortris-8-hydroxyquinoline aluminum (Alq3).

The light efficiency (e.g., the efficiency at which light is emitted) ofsuch a light-emitting portion depends on internal efficiency, and theefficiency of other layers of the EL display device (externalefficiency). A layer's internal efficiency varies depending on thephotoelectric conversion efficiency of the material of which the organiclight-emitting portion is composed. Similarly, external efficiencyvaries depending on the refractive index of each layer of the organic ELdisplay device. The external efficiency is also called light couplingefficiency. A problem is that external efficiency is reduced when lightemitted from the organic light-emitting layer has an outgoing anglegreater than a critical angle of one of the layers. When this happens,reflection occurs at the surface of the layer. Reflection reduces thelight, and causes it to emit externally.

Table 1 illustratively shows the light coupling efficiency of atransparent substrate formed of glass and an electrode layer formed ofindium-tin-oxide (ITO), for each of blue (B), red (R), and green (G)light. The light coupling efficiency is calculated from the refractiveindex of each layer, and N_(in) and N_(out) indicate the refractiveindex of the layer where the light enters and emits, respectively.

TABLE 1 Blue Emitting Red Emitting Green Emitting Layer Layer Layer WaveLength (nm) 450 620 530 Electrode Layer 2.01 1.76 1.93 Refractive Index(N) Substrate Refractive 1.525 1.515 1.52 Index (N) Light Coupling 29%37% 34% Efficiency

It can be seen from Table 1 that the light generated from each emittinglayer may be reduced by more than 60% due to the refractive indexdifference between the electrode layer and the substrate. Variousmethods have been presented to increase such light coupling efficiency.

For example, the Japanese Patent Publication Gazette No. Hei 11-283751discloses a structure that includes a diffraction grating or zone plateformed on a substrate. This reference also discloses diffracted lightleaving an organic film and an Indium Tin Oxide (ITO) electrode.

In such an organic EL device, since irregularities occur on a surface ofa substrate, a fine electrode pattern layer, or a separate diffractiongrating must be included. This requirement complicates the manufacturingprocess, making it difficult to attain efficient productivity. Also, theformation of an organic layer on the irregularities in the surface ofthe substrate or the fine electrode pattern layer increases the overallroughness of the organic layer, which increases current leakage. Currentleakage, in turn, deteriorates the durability and reliability of theorganic EL device.

An organic EL display device preventing a decrease of light couplingefficiency is disclosed in the Japanese Patent Publication Gazette No.Sho 63-17269. The disclosed organic EL display device includes asubstrate having light condensers, such as projecting lenses.

Another organic EL display device is disclosed in the Japanese PatentPublication Gazette No. Hei 1-29394. The display includes a firstdielectric layer interposed between a transparent electrode layer and anemitting layer. Additionally, a second dielectric layer having arefractive index less than that of the first dielectric layer andgreater than that of the transparent electrode layer is also disclosed.

FIG. 1 is a partial cross-sectional view of a conventional organic ELdisplay device. As shown, an organic light emitting portion includingtwo electrode layers 21 and 22 is formed on a substrate (not shown), anda sealing substrate 10 is formed on a photonic crystal layer 41. Aspatial layer 40 formed between the photonic crystal layer 41 and anorganic light-emitting portion is either a vacuum or is filled with aninert gas.

Use of the photonic crystal layer 41 may increase light couplingefficiency, however the path along which light travels must bestructurally even. Otherwise screen display quality degrades. In orderto achieve a uniform screen display quality, the spatial layers 40should be regularly spaced in the regions where the light of an organicEL display device travels. However, such constraints limit the designand manufacture of EL display devices. Such problems also apply toactive matrix (AM) organic EL display devices.

SUMMARY OF THE INVENTION

The invention is directed to an organic electroluminescent (EL) displaydevice having an improved light extracting efficiency due to a photoniccrystal layer formed proximate one side of an organic light-emittingportion. The invention is further directed to a thermal transfer donorfilm used in manufacturing an organic EL display device which has animproved light extracting efficiency.

According to an aspect of the present invention, there is provided anorganic EL display device, which includes a substrate. A first electrodelayer is formed in a predetermined pattern on the substrate. A stack isalso formed on the substrate that includes: a first electrode layer, andan organic light emitting portion formed on the first electrode layer. Aphotonic crystal layer formed directly on the stack increases the lightextracting efficiency of the light-emitting portion.

According to another aspect of the present invention, an organic ELdisplay device may include a photonic crystal layer having a pluralityof protrusions. The protrusions may face the stack or may face away fromit. Additionally, recessed portions formed between the protrusions maybe in a vacuum state or filled with a predetermined gas. Additionally,the recessed portions may be filled with a material having a differentrefractive index than the material of which the protrusions arecomposed.

In another embodiment, an organic EL display device includes a photoniccrystal layer having a plurality of piercing holes, which may be in avacuum state or filled with a predetermined gas. Additionally, theplurality of piercing holes may be filled with a material having adifferent refractive index that the material of which the photoniccrystal layer is composed.

According to another aspect of the present invention, there is providedan organic EL display device which includes a substrate. A stack formedon the substrate includes: a first electrode layer formed with apredetermined pattern on the substrate; a second electrode layer and anorganic light-emitting portion formed on the first electrode layer; aphotonic crystal layer that increases a light extraction efficiency ofthe light-emitting portion; a refractive layer interposed between thephotonic crystal layer and the stack such that the refractive layer isformed directly on the stack. In one embodiment, the refractive layermay be a material having a different refractive index than the materialof which the photonic crystal layer is composed.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the present inventionwill become more apparent by describing in detail exemplary embodimentsthereof with reference to the attached drawings.

FIG. 1 is a partial cross-sectional view of a general organicelectroluminescent (EL) display device.

FIGS. 2A, 2B, 2C, and 2D are partial cross-sectional views of an organicEL display device according to embodiments of the present invention.

FIGS. 3A and 3B are partial cross-sectional views of an organic ELdisplay device according to embodiments of the present invention.

FIGS. 3C and 3D are partial cross-sectional views of an organic ELdisplay device according to the embodiments of the present invention.

FIG. 4 is an organic EL display device according to another embodimentof the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The claimed invention relates to an improved electroluminescent (EL)display device having an improved efficiency of light transmission byuse of a refractive material and a photonic crystal layer. The inventionis further directed to a thermal transfer layer which is used to buildthe photonic crystal layer and to transfer it to an upper surface of thestack.

FIGS. 2A through 2D are cross sectional views of an organicelectroluminescent (EL) display device according to embodiments of thepresent invention. The organic EL display device according to anembodiment of the present invention includes a substrate 210, on which afirst electrode layer 230 is formed in a pattern. An organiclight-emitting portion 240 is formed on the first electrode layer. Asecond electrode layer 250 is formed on the organic light emittingportion 240. A photonic crystal layer 260 which increases the lightextraction efficiency of an organic light-emitting is formed on thesecond electrode 250.

The first electrode layer 230 acts as an anode and the second electrodelayer 250 acts as a cathode, however, the present invention is notlimited to such a structure and can employ a different structure. Thefirst electrode layer 230 may be composed of a transparent conductivematerial such as ITO formed by vacuum deposition or sputtering. Thesecond electrode layer 250 may be composed of magnesium, lithium, orother element having a small work function. Alternatively, the electrodelayer 250 may be a conductive metal such as aluminum, an aluminumcompound, silver, a silver compound, etc.

The organic light-emitting portion 240, interposed between the firstelectrode layer 230 and second electrode layer 250, may further include:a hole injection layer, a hole transportation layer, R, G, B emittinglayers, an electron injection layer, and an electron transportationlayer. Illustrative placements of these layers are shown in FIG. 4.

According to on embodiment of the present invention, a portion of thephotonic crystal layer 260 of the organic EL display device is arrangedproximate the stack so that it is firmly in contact with one side of thestack. In this particular embodiment, there are no spatial layers formedbetween the photonic crystal layer 260 and stack.

The photonic crystal layer 260 may be formed of organic materials andinorganic materials. For example, the photonic crystal layer 260 may becomposed of a photoresist (PR) or a transparent organic material, whichis capable of heat transfer, and which has a molecular weight less than100,000. Alternatively, the photonic crystal layer 260 may be composedof one or more of SiO_(x), SiN_(x), Si₃N₄, TiO₂, MgO, ZnO, Al₂O₃, SnO₂,In₂O₃, MGF₂, and CaF₂. When using an organic material with a molecularweight greater than 100,000 in the photonic crystal layer 260, thephotonic crystal layer 260 may be partially ripped off in a laserinduced thermal imaging process. Thus, depending on the embodiment, thephotonic crystal layer 260 may be smoothly or non-smoothly detached froma thermal imaging film to adhere to a top surface of a stack.

The photonic crystal layer 260 may have various forms, and as shown inFIG. 2A, protrusions 260 b may protrude from one side of the base layer260 a. The protrusions 260 b may protrude from a side facing the stack.Alternatively, although not shown in FIG. 2A, the protrusions 260 b mayprotrude away from the stack. As shown in FIG. 2A, when the protrusions260 b protrude toward the stack, they may firmly contact one side of thesecond electrode layer 250.

When the photonic crystal layer 260 has protrusions 260 b, recessedportions 260 c are formed between the protrusions 260 b, and theserecessed portions 260 c may be maintained as a vacuum state.Alternatively, as shown in FIG. 2B, the recesses 260 c may be filledwith a predetermined inert gas for example, Ne, He, etc. Diffractionoccurs in the photonic crystal layer by alternately arranging differentstates and/or different materials in the individual recesses 260 c. Forexample, all of the recesses may be in a vacuum state or filled with agas. Alternatively, at least one recess may be filled with gas while atleast one other recess is maintained in a vacuum state. The variouscombinations that may be formed are significant. Although not describedhere for brevity's sake, all such combinations are to be construed asbeing within the scope of the claimed invention.

In an alternate embodiment shown in FIG. 2D, diffraction may beincreased by filling the recessed portion 260 c formed with a material,or combination of materials, that have a different refractive index fromthe material which composes the protrusions 260 b. For example, asuitable filler material may be chosen from various organic materialsand inorganic materials such as SiN_(x), TiO₂, etc. If the materialfilling the recessed portion 260 c is to adhere to one side of the stack(for example, the second electrode layer 250), an organic material maybe used as the material filling the recessed portion 260 c to increasethe contactability of the contact surfaces. Additionally, the base layer260 a may be composed of an inorganic material to increase thecontactability between the base layer 260 a and the recessed portion 260c.

In another embodiment of the present invention, as shown in FIG. 2C, thephotonic crystal layer 260 may be a photonic crystal layer with a dotformat in which a plurality of piercing holes 260 d are formed in thebase layer 260 a. The piercing holes 260 d may be arranged at regularintervals within the base layer 260 a, and on one side of the stack.Additionally, when arranged proximate one side of the second electrodelayer 250, the piercing holes 260 d may be maintained in a vacuum state,or may be filled with a designated gas, for example, an inert gas suchas Ne, He, etc.

Additionally, like the organic EL device shown in FIG. 2D, therefractive index may be increased by filling the piercing holes 260 d ofthe photonic crystal layer 260 with a material having a differentrefractive index from the refractive index of the material of which thebase layer 260 a is composed. For example, the piercing holes 260 d maybe filled with an organic material or an inorganic material such asSiN_(x), or TiO₂, etc. Because the material filling the piercing holes260 d should adhere to one side of the stack (for example, the secondelectrode layer 250), the material filling the piercing holes 260 d maybe an organic material that increases the contactability between thesecond electrode layer 250 and the photonic crystal layer 260.Additionally, the base layer 260 a of the photonic crystal layer 260 maybe composed of an organic material to increase the contactabilitybetween the material filling the piercing holes 260 d and the base layer260 a.

Partial cross-sectional views of an active driving EL display deviceaccording to an embodiment of the present invention are shown in FIGS.3A and 3B. As illustrated, buffer layer 311 may be formed on a substrate310 of the EL display device 300. One or more thin film transistors(TFT) for driving pixel forming portions, and one or more drivingportions, each having a capacitor, may be arranged on top of the bufferlayer 311 to produce pixels.

Buffer layer 311 may be formed of a material such as SiO2 by plasmaenhanced chemical vapor deposition. However, the buffer layer 311 may beformed of other materials using other manufacturing processes. Thedriving portion includes a TFT and a capacitor. The TFT also includes: ap- or n-type semiconductor layer 321 formed on part of the buffer layer311; a gate insulating layer 322 formed on the semiconductor layer 321and the buffer layer 311; a gate electrode layer 323 formed on part ofthe gate insulating layer 322 above the p- or n-type semiconductor layer321; and a first insulating layer 324 formed on the a gate insulatinglayer 322 and a gate electrode layer 323. The drain electrode 325 and asource electrode 326 are formed on the first insulating layer 324 andextend down to the semiconductor layer 321 via contact holes 325 a,which pierce through the first insulating layer 324 and the gateinsulating layer 322. The capacitor comprises a first auxiliaryelectrode 327 a which extends from the source electrode 326, and asecond auxiliary electrode 327 b which is arranged on one side of thegate insulating layer 322 corresponding to the first auxiliary electrode327 a and is buried by the first insulating layer 324. A secondinsulating layer 328 buries the TFT and capacitor, that is, the drainelectrode 325, the source electrode 326, and the first auxiliaryelectrode 327 a.

A pixel forming portion is formed on the driving portion to producepixels. The organic light-emitting portion includes the drain electrode325. The first electrode layer 331 (acting as an anode pole) and thesecond electrode layer 343 are formed on the second insulating layer 328which buries the source electrode 326 and the first insulating layer324. The organic light-emitting portion also includes a second electrodelayer 343 as a cathode pole, and an organic light-emitting portion 342interposed between a first electrode layer 331 and the second electrodelayer 343. The present embodiment further includes a passivation layer344 protecting the organic light-emitting portion 342 and preventing theorganic light-emitting portion 342 from deteriorating by absorbingmoisture. The first electrode layer 331 comprises a conductiveconnecting portion 331 a,which contacts one end of the drain electrode325 via a piercing hole formed in the second insulating layer 328.

Referring to FIG. 3A, the method of manufacturing an organic EL displaydevice according to an embodiment of the present invention begins withaccumulatively forming the driving portion and the pixel region on thesubstrate 310.

As mentioned previously, the claimed invention is further directed to athermal transfer donor film used to prepare the photonic crystal layerand adhere the photonic crystal layer to the stack via thermal imaging.In one embodiment, a laser transfer donor film is manufactured bysequentially forming a photothermal conversion layer 371 and a photoniccrystal layer 360 below an imaging base substrate 372. The imaging basesubstrate 372 may be composed of a polymolecule film including apolymolecule material, and the polymolecule film may be composed of apolymolecule material such as polycarbonate, polyethylene terephthalate,polyester, poly acryl, poly epoxy, polyethylene, or polystyrene, etc.The photothermal conversion layer 371 converts light energy of the laserbeam into thermal energy and can be composed of a polymer material suchas carbon black and black lead, a metal such as aluminum or an aluminumoxide product.

Although not shown in the drawings, a separate interior layer composedof acryl may be formed to protect the photothermal conversion layer 371and an exfoliating layer may be formed for the smooth exfoliation of thetransfer portion and to prevent the transferring of the photothermalconversion layer 371 material on one side of the photothermal layer. Thethermal transfer donor film is not limited to this and may be employedin various versions within a range of including a photonic crystal layeror excluding a photothermal conversion layer. The thermal transfer donorfilm has been described in specific embodiments of the presentinvention, however, the thermal transfer donor film may take othervarious forms, and may include a photonic crystal layer, according tothe embodiment of the present invention.

The photonic crystal layer 360 is closely formed directly below thephotothermal conversion layer 371 in FIG. 3A and may be composed of anorganic material having a thickness of several μm or of one or more fromthe group of consisting SiO_(x), SiN_(x), Si₃N₄, TiO₂, MgO, ZnO, Al₂O₃,SnO₂, In₂O₃, MGF₂ and CaF₂. The photonic crystal layer 360 may be formedby thermal compression using a photonic crystal mold that uses Nicoating. The photonic crystal layer 360 has a base layer 360 a and aplurality of protrusions 360 b, which may face the substrate 310. Thebase layer 360 a of the photonic crystal layer 360 may be a thin filmand the protrusions 360 b may form recessed portions or piercing holes.The recessed portions may be in a vacuum state, filled with apredetermined gas such as an inert gas, or filled with a material havinga different refractive index than the material of which the protrusions360 b is composed (refer to FIGS. 3C and 3D). In addition, theprotrusions 360 b and base layer 360 a may be composed of differentmaterials or identical materials.

After the photonic crystal layer 360 is formed on the thermal transferdonor film, the refractive layer 350, which is composed of an organicmaterial or one or more inorganic materials such as SiN_(x) and TiO₂,may be formed below the photonic crystal layer 360. In addition, therefractive layer 350 may be planarized to prevent a bad connection withone side of the stack due to an uneven surface. The refractive layer 350may have protrusions that correspond to the recessed portions formed bythe protrusions 360 b. When the protrusions 360 b face the substrate310, a structure which engages with the recessed portion formed by theprotrusions may be adopted. The protrusions 360 b are not limited tothese structures, and the protrusions 360 b may be formed on the side ofthe photonic crystal layer 360 opposite the refractive layer 350 of thephotonic crystal layer.

In addition, although not shown in the drawings, when the photoniccrystal layer is a dot type having a plurality of piercing holes, theprotrusions formed on the one side facing the photonic crystal layer mayhave a structure that engages with the piercing holes. To increasediffraction and prevent possible defects when the photonic crystal layeris formed, the refractive layer 350, which is formed directly below thephotonic crystal layer 360, should be composed of different elementsthan the photonic crystal layer. Additionally, the refractive index ofthe base layer 360 a of the photonic crystal layer 360 should bedifferent from the refractive index of the refractive layer 350.

After preparing the thermal transfer donor film, which includes thephotonic crystal layer, the photonic crystal layer 360 is thermallyimaged onto a surface of the stack. For example, the thermal transferdonor film is placed close to the upper surface of the EL display device300 such that the lower surface of the thermal transfer donor film facesthe upper surface of the EL display device 300.

Heat is then applied to the imaging base substrate using a heat bar,electron inductive heating, ultrasound friction heating, or a laser.Laser beams may be used due to their high precision. Thus, in oneembodiment, a laser irradiation source irradiates a laser beam onto adesired region of the imaging base substrate 372. The irradiated laserbeam passes through the transparent imaging base substrate and deliversenergy to the photothermal conversion layer 371, which may be carbonblack layers or similar layers. The photothermal conversion layer 371converts the light energy of the irradiated laser beam to heat energyand detaches the photonic crystal layer 360 from the photothermalconversion layer 371. As shown in FIG. 3B, the detached photonic crystallayer 360 and refractive layer 350, etc. are transferred to one side ofthe pixel region of the EL display device 300 (e.g., on the passivationlayer 344), and no spatial layer is formed between the photonic crystallayer 360 and the passivation layer 344. In addition, for example, whenthe passivation layer 344 is composed of an inorganic material such asSiO₂, SiN_(x), etc., adherence with the passivation layer 344 may beincreased by forming the refractive layer 350 of an organic material andthe base layer 360 a of an inorganic material.

In another embodiment shown in FIG. 3C, the refractive layer 350 is notincluded on one side of the photonic crystal layer 360 so that at leasta portion of the photonic crystal layer 360 is formed directly on thepassivation layer 344. The recessed portions 360 c formed by theprotrusions 360 b may be maintained in a vacuum state, filled with adesignated gas, or may be filled with a material having a differentrefractive index from the material of which the protrusions 360 b iscomposed (refer to FIG. 3D). The photonic crystal layer 360 may be a dottype photonic crystal layer with a plurality of piercing holes formed inthe base layer, which may be maintained in a vacuum state, filled withdesignated gas, or filled with a material having a different refractiveindex than the base layer.

An EL display device according to another embodiment of the presentinvention is shown in FIG. 4. The first electrode layer 421 is formed ona substrate 410. An electron injection layer 422, an electrontransportation layer 423, an organic light-emitting portion including R,G, and B light-emitting layers, 425 a, 425 b, and 425 c, an electrontransportation layer 424, and a second electrode layer 426 aresequentially formed on the substrate 410 and the previously installedfirst electrode layer 421. A passivation layer 430 may be formed on topto protect the organic light-emitting portion.

In addition, photonic crystal layers 450 are formed on the passivationlayer 430 and refractive layers 440 may be formed between the photoniccrystal layers 450 and the passivation layer 430. Because thewavelengths of the light emitting from the R, G, and B light-emittinglayers, 425 a, 425 b, and 425 c differ, the photonic crystal layers 450a, 450 b, and 450 c may be individually configured to correspond to therespective wavelengths of colored light. Thus, in one embodiment, thephotonic crystal layers 450 formed on the passivation layer 430 are eachcustom patterned according to the types of light-emitting layers 425 a,425 b, and 425 c, (e.g., per one of colors R, G, or B).

Patterns may be made according to the sub-pixel group corresponding tothe color R, the sub-pixel group corresponding to the color G, and thesub-pixel group corresponding to the color B. In one embodiment, theforms of photonic crystal layers within a sub-pixel group are differentthan the forms of the photonic crystal layers of any one of the othersub-pixel groups. In some cases, the photonic crystal layers within anidentical group can have different forms or measurements.

Meanwhile, referring to 2A, FIG. 2B, FIG. 2C, FIG. 2D, FIG. 3A, FIG. 3B,FIG. 3C, FIG. 3D, and FIG. 4, the laser thermal transfer donor film mayinclude a photothermal conversion layer. It may further include aphotonic crystal layer which has a plurality of protrusions.Additionally included may be a plurality of piercing holes formed on thetransfer donor film. The laser thermal transfer donor film may alsoinclude a refractive layer composed of a material having a differentrefractive index from that of a material that composes one side of thephotonic crystal layer which is the furthest from the photothermalconversion layer of the photonic crystal layer. In addition, thephotonic crystal layer formed on the laser thermal transfer donor filmmay be formed in a plurality of groups, and the measurements andphysical properties of the photonic crystal layer of the groups may bedifferent for different groups.

The above-described embodiments are described in terms of a passivedriving type or an active driving type organic EL display device,however, the present invention is not limited to any one type.

The present invention with the above-described structure has thefollowing effects.

According to embodiments of the present invention, the organic ELdisplay device does not include spatial layers between a photoniccrystal layer and a stack. Additionally, forming the photonic crystallayer on the stack improves light extraction efficiency, and solvesphysical problems in the manufacturing process by obviating the need tomanufacture spatial layers between the photonic crystal layer and stack.

Efficiency of light extraction is further improved by including arefractive layer with the photonic crystal layer. Additionally, photoniccrystal layers, which are individually formed for respective R, G, and Bgroups, can increase the light extraction efficiency for each wavelengthof colored light emitted.

Embodiments of the organic EL display device and thermal transfer donorfilm described herein enable precise manufacturing using a thermalimaging method, especially a laser induced thermal imaging (LITI)method. Use of such a process significantly reduces manufacturing costsand time by eliminating the need to form spatial layers, which was aproblem in the conventional manufacturing of an organic EL displaydevice.

The various embodiments of the present invention may apply to not only apassive driving matrix (PM) organic EL display device, but also to anactive driving (AM) organic EL display device.

While the present invention has been particularly shown and describedwith reference to exemplary embodiments thereof, it will be understoodby those of ordinary skill in the art that various changes in form anddetails may be made therein without departing from the spirit and scopeof the present invention as defined by the following claims.

1. A thermal transfer donor film comprising: a thermal imaging basefilm; a photothermal conversion layer below the base film; anintermediate layer formed below the photothermal conversion layer; and aphotonic crystal layer formed below the intermediate layer.
 2. Thethermal transfer donor film of claim 1, wherein the photonic crystallayer has a plurality of protrusions.
 3. The thermal transfer donor filmof claim 1, wherein the photonic crystal layer has a plurality ofpiercing holes.
 4. The thermal transfer donor film of claim 1, wherein arefractive layer composed of a material having a different refractiveindex than the material of which the photonic crystal layer is composedis formed under the photonic crystal layer.